section 3.2 Flashcards
The smallest unit of matter that retains the properties of an element and cannot be divided by chemical means.
Who first introduced the idea of indivisible particles?
Maharishi Kanad (India) and Democritus (Greece).
Who gave the first scientific theory about atoms?
John Dalton.
State any two postulates of Dalton’s Atomic Theory.
- All matter is made up of indivisible atoms.
- Atoms of the same element are identical in mass and properties.
What is the symbol for Sodium and its Latin name?
Symbol: Na, Latin Name: Natrium.
How are symbols of elements written?
First letter capital, second letter (if present) lowercase.
Example: He for Helium.
What is atomic mass?
The average mass of an atom compared to 1/12th of the mass of a carbon-12 atom.
What is the unit of atomic mass?
Unified mass unit (u or amu).
What is the atomic mass of Oxygen?
16 u
Name one monoatomic element and one diatomic molecule.
Monoatomic: Helium (He), Diatomic: Oxygen (O₂)
How do atoms exist in nature?
As monoatomic (noble gases), molecules of elements (O₂, H₂), or molecules of compounds (H₂O, CO₂).
What makes atoms combine with others?
To gain stability by forming molecules or compounds.
